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Rapid communications in mass spectrometry : RCM

Gas chromatography/mass spectrometry measurement of xenon in gas-loaded liposomes for neuroprotective applications.


PMID 27689777

Abstract

We have produced a liposomal formulation of xenon (Xe-ELIP) as a neuroprotectant for inhibition of brain damage in stroke patients. This mandates development of a reliable assay to measure the amount of dissolved xenon released from Xe-ELIP in water and blood samples. Gas chromatography/mass spectrometry (GC/MS) was used to quantify xenon gas released into the headspace of vials containing Xe-ELIP samples in water or blood. In order to determine blood concentration of xenon in vivo after Xe-ELIP administration, 6xa0mg of Xe-ELIP lipid was infused intravenously into rats. Blood samples were drawn directly from a catheterized right carotid artery. After introduction of the samples, each vial was allowed to equilibrate to 37°C in a water bath, followed by 20xa0minutes of sonication prior to headspace sampling. Xenon concentrations were calculated from a gas dose-response curve and normalized using the published xenon water-gas solubility coefficient. The mean corrected percent of xenon from Xe-ELIP released into water was 3.87xa0±xa00.56% (SD, nxa0=xa08), corresponding to 19.3xa0±xa02.8xa0μL/mg lipid, which is consistent with previous independent Xe-ELIP measurements. The corresponding xenon content of Xe-ELIP in rat blood was 23.38xa0±xa07.36xa0μL/mg lipid (nxa0=xa08). Mean rat blood xenon concentration after intravenous administration of Xe-ELIP was 14xa0±xa010xa0μM, which is approximately 15% of the estimated neuroprotective level. Using this approach, we have established a reproducible method for measuring dissolved xenon in fluids. These measurements have established that neuroprotective effects can be elicited by less than 20% of the calculated neuroprotective xenon blood concentration. More work will have to be done to establish the protective xenon pharmacokinetic range. Copyright © 2016 John Wiley & Sons, Ltd.

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